diff --git a/README.md b/README.md
index 52be4d5..a69da1b 100644
--- a/README.md
+++ b/README.md
@@ -91,6 +91,11 @@ EXAMPLES
 BUGS
 	Report bugs at https://github.com/pascaldekloe/colfer/issues
 
+	Text validation is not part of the marshalling and unmarshalling
+	process. C and Go just pass any malformed UTF-8 characters. Java
+	and JavaScript replace unmappable content with the '?' character
+	(ASCII 63).
+
 SEE ALSO
 	protoc(1)
 ```
diff --git a/cmd/colf/main.go b/cmd/colf/main.go
index 8fe9841..0681e3a 100644
--- a/cmd/colf/main.go
+++ b/cmd/colf/main.go
@@ -178,6 +178,10 @@ func init() {
 	tail += "\t\t" + cmd + " -p com/example -x com/example/Parent Java api\n"
 	tail += "\n" + bold + "BUGS" + clear + "\n"
 	tail += "\tReport bugs at https://github.com/pascaldekloe/colfer/issues\n\n"
+	tail += "\tText validation is not part of the marshalling and unmarshalling\n"
+	tail += "\tprocess. C and Go just pass any malformed UTF-8 characters. Java\n"
+	tail += "\tand JavaScript replace unmappable content with the '?' character\n"
+	tail += "\t(ASCII 63).\n\n"
 	tail += bold + "SEE ALSO\n\t" + clear + "protoc(1)\n"
 
 	flag.Usage = func() {
diff --git a/ecma.go b/ecma.go
index c58b999..080e1c1 100644
--- a/ecma.go
+++ b/ecma.go
@@ -136,15 +136,20 @@ var {{.NameNative}} = new function() {
 				bytes[i++] = c >> 6 | 192;
 			} else {
 				if (c > 0xd7ff && c < 0xdc00) {
-					if (++ci == s.length) fail('UTF-8 encode: incomplete surrogate pair');
+					if (++ci == s.length) {
+						bytes[i++] = 63;
+						continue;
+					}
 					var c2 = s.charCodeAt(ci);
-					if (c2 < 0xdc00 || c2 > 0xdfff) fail('UTF-8 encode: second char code 0x' + c2.toString(16) + ' at index ' + ci + ' in surrogate pair out of range');
+					if (c2 < 0xdc00 || c2 > 0xdfff) {
+						bytes[i++] = 63;
+						--ci;
+						continue;
+					}
 					c = 0x10000 + ((c & 0x03ff) << 10) + (c2 & 0x03ff);
 					bytes[i++] = c >> 18 | 240;
 					bytes[i++] = c>> 12 & 63 | 128;
-				} else { // c <= 0xffff
-					bytes[i++] = c >> 12 | 224;
-				}
+				} else bytes[i++] = c >> 12 | 224;
 				bytes[i++] = c >> 6 & 63 | 128;
 			}
 			bytes[i++] = c & 63 | 128;
@@ -159,24 +164,21 @@ var {{.NameNative}} = new function() {
 			var c = bytes[i++];
 			if (c > 127) {
 				if (c > 191 && c < 224) {
-					if (i >= bytes.length) fail('UTF-8 decode: incomplete 2-byte sequence');
-					c = (c & 31) << 6 | bytes[i] & 63;
+					c = (i >= bytes.length) ? 63 : (c & 31) << 6 | bytes[i++] & 63;
 				} else if (c > 223 && c < 240) {
-					if (i + 1 >= bytes.length) fail('UTF-8 decode: incomplete 3-byte sequence');
-					c = (c & 15) << 12 | (bytes[i] & 63) << 6 | bytes[++i] & 63;
+					c = (i + 1 >= bytes.length) ? 63 : (c & 15) << 12 | (bytes[i++] & 63) << 6 | bytes[i++] & 63;
 				} else if (c > 239 && c < 248) {
-					if (i+2 >= bytes.length) fail('UTF-8 decode: incomplete 4-byte sequence');
-					c = (c & 7) << 18 | (bytes[i] & 63) << 12 | (bytes[++i] & 63) << 6 | bytes[++i] & 63;
-				} else fail('UTF-8 decode: unknown multibyte start 0x' + c.toString(16) + ' at index ' + (i - 1));
-				++i;
+					c = (i+2 >= bytes.length) ? 63 : (c & 7) << 18 | (bytes[i++] & 63) << 12 | (bytes[i++] & 63) << 6 | bytes[i++] & 63;
+				} else c = 63;
 			}
 
 			if (c <= 0xffff) s += String.fromCharCode(c);
-			else if (c <= 0x10ffff) {
+			else if (c > 0x10ffff) s += '?';
+			else {
 				c -= 0x10000;
 				s += String.fromCharCode(c >> 10 | 0xd800)
 				s += String.fromCharCode(c & 0x3FF | 0xdc00)
-			} else fail('UTF-8 decode: code point 0x' + c.toString(16) + ' exceeds UTF-16 reach');
+			}
 		}
 		return s;
 	}
diff --git a/ecma/gen/Colfer.js b/ecma/gen/Colfer.js
index 2d0507c..02d66c1 100644
--- a/ecma/gen/Colfer.js
+++ b/ecma/gen/Colfer.js
@@ -649,15 +649,20 @@ var gen = new function() {
 				bytes[i++] = c >> 6 | 192;
 			} else {
 				if (c > 0xd7ff && c < 0xdc00) {
-					if (++ci == s.length) fail('UTF-8 encode: incomplete surrogate pair');
+					if (++ci == s.length) {
+						bytes[i++] = 63;
+						continue;
+					}
 					var c2 = s.charCodeAt(ci);
-					if (c2 < 0xdc00 || c2 > 0xdfff) fail('UTF-8 encode: second char code 0x' + c2.toString(16) + ' at index ' + ci + ' in surrogate pair out of range');
+					if (c2 < 0xdc00 || c2 > 0xdfff) {
+						bytes[i++] = 63;
+						--ci;
+						continue;
+					}
 					c = 0x10000 + ((c & 0x03ff) << 10) + (c2 & 0x03ff);
 					bytes[i++] = c >> 18 | 240;
 					bytes[i++] = c>> 12 & 63 | 128;
-				} else { // c <= 0xffff
-					bytes[i++] = c >> 12 | 224;
-				}
+				} else bytes[i++] = c >> 12 | 224;
 				bytes[i++] = c >> 6 & 63 | 128;
 			}
 			bytes[i++] = c & 63 | 128;
@@ -672,24 +677,21 @@ var gen = new function() {
 			var c = bytes[i++];
 			if (c > 127) {
 				if (c > 191 && c < 224) {
-					if (i >= bytes.length) fail('UTF-8 decode: incomplete 2-byte sequence');
-					c = (c & 31) << 6 | bytes[i] & 63;
+					c = (i >= bytes.length) ? 63 : (c & 31) << 6 | bytes[i++] & 63;
 				} else if (c > 223 && c < 240) {
-					if (i + 1 >= bytes.length) fail('UTF-8 decode: incomplete 3-byte sequence');
-					c = (c & 15) << 12 | (bytes[i] & 63) << 6 | bytes[++i] & 63;
+					c = (i + 1 >= bytes.length) ? 63 : (c & 15) << 12 | (bytes[i++] & 63) << 6 | bytes[i++] & 63;
 				} else if (c > 239 && c < 248) {
-					if (i+2 >= bytes.length) fail('UTF-8 decode: incomplete 4-byte sequence');
-					c = (c & 7) << 18 | (bytes[i] & 63) << 12 | (bytes[++i] & 63) << 6 | bytes[++i] & 63;
-				} else fail('UTF-8 decode: unknown multibyte start 0x' + c.toString(16) + ' at index ' + (i - 1));
-				++i;
+					c = (i+2 >= bytes.length) ? 63 : (c & 7) << 18 | (bytes[i++] & 63) << 12 | (bytes[i++] & 63) << 6 | bytes[i++] & 63;
+				} else c = 63;
 			}
 
 			if (c <= 0xffff) s += String.fromCharCode(c);
-			else if (c <= 0x10ffff) {
+			else if (c > 0x10ffff) s += '?';
+			else {
 				c -= 0x10000;
 				s += String.fromCharCode(c >> 10 | 0xd800)
 				s += String.fromCharCode(c & 0x3FF | 0xdc00)
-			} else fail('UTF-8 decode: code point 0x' + c.toString(16) + ' exceeds UTF-16 reach');
+			}
 		}
 		return s;
 	}